James Snell asked "Where exactly do we draw the lines between the packaging
protocol and the API that utilizes that protocol?"
We draw the line at the protocol.
Interop is based on the protocol, not the API, in the same way that HTML
interop is based on the agreed on grammar, syntax and semantics of HTML, not
on an API. The HTML specification does not prescribe an API.
If there is work on an API, that would be a distinct specification.